1. The Field of the Invention
The invention generally relates to fiber-optic test equipment. More specifically, the invention relates to test equipment for testing optical transmitters used in fiber-optic communications.
2. Description of the Related Art
Fiber-optic networking can be used to communicate in modern high-speed networks. To transmit data on a fiber-optic network, the data is converted from an electronic signal to an optical signal. This conversion may be done, for example, by using a transmitter or transmitting optical subassembly (TOSA). The transmitters and TOSAs often include light generating devices such as a laser or light emitting diode (LED). The light generating device is modulated according to digital data to produce a modulated optical signal.
When optical signals are received, those optical signals are generally converted to an electronic signal. This is often accomplished using a receiver or a receiver optical subassembly (ROSA). Receivers and ROSAs generally include a photo sensitive device such as a photodiode connected to a transimpedance amplifier (TIA). When a modulated optical signal impinges the photo sensitive device, a modulated current is induced in the photo sensitive device. This current can be converted by the TIA to an electronic signal usable by digital devices on a network.
Manufacturers of ROSAs and TOSAs typically perform various performance tests on the ROSAs and TOSAs before they are delivered to distributors and end customers. This performance testing can be used to detect defects or to sort components into groups of different rated values.
More particularly, testing directed towards the ROSA may include testing the responsivity of the ROSA to a modulated optical signal, testing the amount of current produced for a given amount of optical signal and so forth. Testing responsivity includes comparing a modulated optical signal input into the ROSA to an AC electrical signal produced by the ROSA as a result of receiving the AC optical signal.
Testing may be performed on the TOSA to characterize operating characteristics of the TOSA. One test that may be performed includes plotting the amount of optical energy produced by the TOSA as a function of the amount of current and voltage used to drive the TOSA. An LIV (light intensity, current, voltage) curve is one way of graphically illustrating the characteristics of a TOSA or laser or LED source. Another test includes measuring the amount of noise produced by the TOSA.
Many of these tests have conventionally been performed using expensive high-frequency test equipment. For example, some tests use a high frequency communications analyzer costing in the tens of thousands of dollars. Further, many of these test devices are general-purpose test devices. As such, these general purpose devices require significant amounts of human interaction to configure for testing a particular component. This increases the test times for each component. When a number of components are tested, the amount of manpower and equipment to process testing of the components also quickly increases. Thus, testing components, for example, ROSAs and TOSAs, is time consuming and requires properly configured equipment.
Additionally, testing is often not repeatable from part to part. This is due to the changing nature of cables and the like associated with general purpose test equipment. Accordingly, what would be advantageous are more efficient mechanisms for testing optical components.